Alkylation apparatus

ABSTRACT

FLUID HEAT EXCHANGERS COMPRISING TWO U-TUBE BUNDLES DISPOSED WITHIN A COMMON EXTERIOR SHELL WITH THEIR RESPECTIVE BENDS IN AN ADJACENT, MONOVERLAPPING RELATIONSHIP AT THE MID PORTION OF SAID SHELL, WHEREIN MULTIPLE EXCHANGER SHELLS CAN BE PLACED IN A SIDE-BY-SIDE POSITION, JOINED   WITH COMMUNICATING ENTRY AND EXIT FLUID CONDUITS. THE HEAT EXCHANGERS COMMUNICATE THROUGH FLUID OUTLET HEADERS TO TUBULAR REACTORS IN COMBINATION WITH AN ALKYLATION SETTLER.

June 18, 1974 w. F. VERNON 3.317.703

ALKYLATION APPARATUS Filed April 10, 1972 2 Sheets-Sheet 1 FIG. 2

INVENTOR.

W. E VERNON A TTORNEKS" June 18, 1974 w. F. VERNON ALKYLATIOR APPARATUS2 Sheets-Sheet 1 Filed April 10, 1972 United States Patent Otfice3,817,708 Patented June 18, 1974 3,817,708 ALKYLATION APPARATUS WalterF. Vernon, Bartlesville, kla., assignor to Phillips Petroleum CompanyContinuation-impart of abandoned application Ser. No. 14,062, Feb. 25,1970. This application Apr. 10, 1972, Ser. No. 242,542

Int. Cl. C07c 3/54; F28d 7/06 US. Cl. 23260 7 Claims ABSTRACT OF THEDISCLOSURE This application is a continuation-in-part of my copendingapplication Ser. No. 14,062, filed Feb. 25, 1970.

This invention relates to an indirect fluid heat exchanger. In anotheraspect, this invention relates to an arrangement of U-tubes with theirrespective bend portions in an adjacent, nonoverlapping relationshipenclosed in a common exterior shell. In yet another aspect of thisinvention, the heat exchanger shell can be positioned with a secondexchanger in a side-by-side relationship with said shells communicatingthrough common fluid entry and exit conduits. In still another aspectthis invention relates to multiple fluid heat exchangers which providesymmetrical fluid flow to reactor riser tubes.

The chemical processing art of today faces varied problems, many ofwhich are related to efiicient mass transfer and reactant temperaturecontrol. Chemical fluids used in modern production methods often requirestronger process apparatus made from corrosive resistant materials. Forexample, the catalytic alkylation of hydrocarbons requires thecontinuous cyclic transportation of acid catalyst throughout thereaction and recovery system. The problem of handling highly corrosiveacid catalysts such as hydrofluoric or sulfuric acids leads to specialequipment requirements. Special alloy valves, vessels, pumps, and heatexchangers are required in the catalytic acid alkylation of hydrocarbonswhich greatly increases the equipment costs. The effect of temperatureupon an alkylation process is critical and removal from or addition ofheat to the reaction is an essential feature of the process, oftendictating and limiting the design of the alkylation unit to be employed.

The apparatus of my invention provides a heat exchanger system which cangreatly increase the capacity, for example, of an alkylation unit. Asuitable heat transfer media, for example, Water, flows through theU-tubes while an alkylation catalytic acid flows through the remainingspace within the cylindrical shell which houses the U-tubes. Eachcylindrical shell contains two U-tube bundles. The bends of the U-tubesapproach each other near the center of the shell in an adjacent,spaced-apart, nonoverlapping relationship. The bend portions of theU-tubes are connected through the straight tube portions to coolantheaders at the respective ends of the exterior shell. The alkylationcatalytic acid enters the heat exchanger through headers at each end ofthe shell and exits from the center portion of said shell. Twocylindrical shell exchangers of my invention can be joined in aside-by-side relationship and joined with communicating acid entry andexit conduits. The multiple fluid heat exchangers in a sideby-siderelationship can also communicate with a reactor user.

It is an object of this invention to provide a more eflicient masstransfer heat exchanger.

It is another object of this invention to provide an increased heatexchanger capacity while reducing space, equipment, and productioncosts.

It is yet another object of this invention to provide symmetrical flowof cooled alkylation acids to reactor riser tubes from multiple heatexchangers.

The heat exchanger of my invention increases mass transfer and coolingcapacity with a minimum equipment space requirement. The adjoining ofmultiple heat exchangers of my invention reduce cyclic pressure drop,therein increasing fluid flow rates. The symmetrical and shorter flowpatterns achieved through the applications of my invention provide theincreased mass and energy transfer rates required by modern processengineering.

The apparatus, specifically the heat exchangers of the invention, haveapplication in catalytic alkylation processing. For example,hydrofluoric acid alkylation is a process wherein olefins such aspropylene, butylene, or pentene are combined with isobutane in thepresence of hydrofluoric acid catalyst to yield a product in a gasolineboiling range. The product produced is called alkylate. Alkylate isproduced from hydrocarbons which are too light and too volatile for usein gasoline through the hydrofluoric acid catalyzed chemical joining ofthese light hydrocarbons. Hydrofluoric acid alkylation of these lighthydrocarbons produces heat which must be removed in order to controlreaction temperature. Reaction temperature control is achieved throughthe cooling of the hydrofluoric acid before it is mixed with the reactorfeed. Optimum reaction temperature will vary somewhat depending onoperating conditions and character of the olefin feedstock, but atemperature of from about to F. is representative of alkylation reactionprocessing.

A more complete understanding of the invention may be had by referenceto the accompanying drawing wherein:

FIG. 1 is a front elevational view of the heat exchanger of theinvention;

FIG. 2 is a perspective view of another embodiment of the invention; and

FIG. 3 is a diagrammatic illustration of a vertical alkylation reactortube, acid settler, acid rerun conduit, acid cooler, and acid storageprovided in an arrangement which fully exploits the symmetrical acidcooling and flow provided by the apparatus of the invention.

Referring to FIG. 1, a heat exchanger 2 has an outer shell 4. Shell 4has an opening 6 extending longitudinally through its length from afirst end 7 to a second end 9. Shell 4 has an opening 8 at a first endportion 11 and an opening 10 at a second end portion 13. The first end 7of shell 4 has a lower opening 12 and an upper opening 14. The secondend 9 of shell 4 has a lower opening 16 and an upper opening 18. A midportion 20 of the shell 4 has a horizontal opening 22 spaced betweenadjacent, spaced-apart, nonoverlapping bend portions 24 and 26 of theU-tubes 28 and 30. Said U-tubes 28 and 30 have bend portions 24 and 26at the mid portion 20 of shell 4 and straight tube portions 32 and 34extending longitudinally to the first end 7 and the second end 9,respectively through the shell 4 opening 6.

Referring to FIG. 2. the heat exchanger 2 of FIG. 1 is placed with asecond heat exchanger 3 in a side-by-side horizontal arrangement. Thetwo exchangers 2 and 3 are adjoined through the fluid inlet conduits 41and 42. The heat exchangers 2 and 3 are also joined through a commonfluid outlet conduit 45. The heat exchange opening 22 of FIG. 1 is anopen end of outlet conduit 45, positioned between the adjacent,spaced-apart, nonoverlapping U- bends of exchanger 2.

Referring to FIG. 3, the heat exchangers of FIGS. 1 and 2 are arrangedin multiples of two on opposite sides of an acid storage 52 having asettler 50 vertically positioned thereabove. The heat exchangers in aside-by-side horizontal arrangement communicate with tubular reactors 27and 48 on respective side of the acid storage 52 and settler 50 throughfluid outlet conduits 45. The tubular reactors 27 and 48 are incommunication with hydrocarbon feed sources, not shown, through riserconduits 29 and 54 respectively. Acid return conduits 46 flow from theelevated settler 50 acid return header 56 to the common fluid inletconduits 43 shared by the multiple heat exchangers of the invention.

In the operation of the apparatus of FIG. 1, recycle fluid, for example,alkylation catalytic acid, enters the heat exchanger 2 through theopenings 8 and where it is cooled by indirect heat exchange with theheat transfer media which enters the U-tubes 28 and 30 through theopenings 16 and 12, and leaves through openings 14 and 18. The cooledacid flows inwardly to the mid portion 20 opening 22 and then is passedthrough the tubular alkylation reactor 27. There it is contacted byhydrocarbon feed passing through the conduit 29.

In the operation of the apparatus of FIG. 2, recycle alkylation acidenters the heat exchangers 2 and 3 through joining conduits 41 and 43and exits through the communicating conduit 45 to a common flow tubularreactor 27. Cooling fluid enters and exits the four respective ends ofthe two horizontal cylindrical exchanger shells providing indirectcooling for the alkylation acid. FIG. 3 provides a multiple applicationof the apparatus of FIG. 2 and functions accordingly.

Alkylation reactors, settler-acid storage, and hydrofluoric acid coolingsystem of the type illustrated in the drawings is employed for thealkylation of isobutane and light oleflnic hydrocarbons in the presenceof hydrofluoric acid catalyst. The following alkylation apparatus andprocess conditions are for illustrative purposes and are alforded by thesymmetrical flow and energy exchange achieved by the heatexchanger-reactor of the invention. For example, a settler having thedimensions of 26 ft. by 66 ft. in an elevated position would providesufficient capacity for two reactor risers having a 66-inch diameter.The four acid return conduits to the exchangers would need to be about30 inches in diameter since the hydrofluoric acid to hydrocarbon feedpreferably varies from about 4:1 to about 6:1 by liquid volume. The heatexchangers would correspondingly have the approximate dimensions of55-inch diameter shells having total lengths of about 80 ft. Apparatusof these dimensions can accommodate about 50,000 barrels per day of newhydrocarbon feed and 227,135 barrels per day of recycle feed at atemperature of about 95 F. The return acid temperature to the exchangersis about 95 F. and is lowered to about 86 F. through energy exchange.

The hydrofluoric acid alkylation apparatus of my invention provides aself-circulating acid cooling system which requires equal material flowin order to achieve the expanded flow demands as illustrated in thefollowing table:

TABLE-BARRELB PER DAY It is readily apparent from the above volumes thatequal flow of acid through the exchangers and communicating riserreactors is critical. Self-circulating volume and energy transferapparatus of this magnitude places such a demand on heat exchangercapacity that design limitations have in the past limited the overallvolume of the alkylation unit. The apparatus of FIGS. 1, 2 and 3 affordsan equal and balanced acid flow demanded by modern al kylation processengineering.

The apparatus of FIGS. 1 and 2 can be duplicated as needed throughapplications of multiples of two U-tube exchanger units as enclosed intheir common exterior shells, for example, as shown in FIG. 3. Othervariations and modifications are also possible within the scope of thisdisclosure without departing from the scope and spirit thereof.

What I claim is:

1. A fluid heat exchanger comprising: an elongated shell, at least onepair of U-tubes disposed within said shell with respective bends inadjacent, spaced-apart, nonoverlapping relationship at a center portionof said shell, an inlet and outlet leader connected to each U-tube ateach end of said shell, fluid inlet headers connected to the ends ofsaid shell and a fluid outlet header connected to the center portion ofsaid shell between the adjacent, spaced apart, nonoverlapping bends ofthe U-tubes, said fluid headers in relation to said shell to directfluid flow in a path along the length of said U-tubes.

2. A fluid heat exchanger according to claim 1 wherein the fluid outletheader connected to the mid portion of said heat exchanger shellcommunicates with a tubular reactor.

3. A fluid heat exchanger according to claim 1 wherein at least two ofthe heat exchangers are positioned in a side-by-side relationship withthe heat exchangers communicating through common fluid inlet and outletmeans.

4. A fluid heat exchanger according to claim 3 wherein the heatexchangers communicate through the common fluid outlet means with atubular reactor.

5. Fluid heat exchanger-tubular reactor apparatus comprising, incombination: a pair of elongated shells having at least one pair ofU-tubes disposed within each of the shells with respective heads inadjacent, spaced-apart, nonoverlapping relationship at center portionsof said shells; inlet and outlet headers connected to each U-tube ateach end of said shells; fluid inlet headers connected to the ends ofsaid shells and fluid outlet headers connected to the center portions ofsaid shells between the adjacent, nonoverlapping, spaced-apart bends ofthe U- tubes, said fluid headers in relation to said shell to directfluid flow in a path along the length of said U-tubes; and a tubularreactor spaced between the elongated shells in communication with thefluid outlet headers and an alkylation settler.

6. The apparatus according to claim 5 wherein at least two pairs offluid heat exchangers are positioned in paired side-by-side relationshipwith a first pair of heat exchangers communicating through common fluidinlet and Riser reactor Riser hydrofluoric reactor acid feed at Hydro-Recyele hydroa 4:1 liquid carbon isocsrbon volume Material componentsteed butane teed ratio settler-to exchanger return hydrofluoric acidPentene plus .2:

Total barrels per dayoutlet means with the alkylation settler and afirst reactor riser on one side of the settler; and a second pair ofheat exchangers communicating through common fluid inlet and outet meanswith the alkylation settler and a second reactor riser on another sideof the settler.

7. The apparatus according to claim 6 wherein the settler communicatesthrough four equal flow acid return conduits with the common inlet meansof the heat exchangers.

References Cited UNITED STATES PATENTS 3,169,153 2/1965 Walker et a1.260-68148 3,212,860 10/1965 Vernon 260683.48

6 3,246,047 4/1966 Chapman et a]. 260683.48 3,281,213 10/1966 Waddill260--683.48 3,544,651 12/1970 Chapman 260683.48

US. Cl. X.R. 23285; 16S143, 158; 260683.48

